LCDs are gaining popularity in recent years. Also, more LCDs having a larger screen size are commercially available. Further, applications of LCD are diversified. A typical application thereof is LCD TV (television). It is understood that light intensity of LCD background is required to increase for improving video quality as the screen size of LCD increases. Accordingly, more lamps (e.g., fluorescent lamps) are mounted in LCD for providing a sufficient light intensity of LCD background.
Conventionally, frequency synchronization among a plurality of lamps is required in controlling the operation of LCD lamps. Otherwise, a difference frequency distortion may occur between any two adjacent lamps, resulting in a flickering of the LCD screen.
Typically, ICs (integrated circuits) are used for controlling a frequency synchronization operation of the plurality of lamps. Such controlling is called active synchronous drive. The provision of a plurality of ICs is for the purpose of carrying out frequency synchronization among the lamps in operation. In detail, the ICs operate to output driving signals of the same frequency to respective lamps so that all lamps can operate in the same frequency.
A well known frequency synchronization device for an LCD having a plurality of LCDs (three as shown) is shown in FIG. 1. For any single lamp (e.g., first lamp 14a) (i.e., single lamp operation implementation), associated components such as a control element 11a, a driving element 12a, and a first power amplification unit 13a are provided. The control element 11a is adapted to control current of the first lamp 14a and provide protection against open circuit. Output signals of the control element 11a are sent to the first power amplification unit 13a for driving via the driving channel 12a. The first power amplification unit 13a comprises a DC (direct current) power 131a, a first power switch 132a, and a transformer 133a in which the first power switch 132a is adapted to convert DC into AC (alternating current) prior to outputting to the transformer 133a, and the transformer 133a is adapted to boost the AC voltage for activating the first lamp 14a. Each of the control elements 11a, 11b and 11c is implemented as an IC. Further, a synchronous signal bus 10 is provided to connect all of the control elements 11a, 11b and 11c together while providing synchronous signals thereto. Thus, all lamps 14a, 14b and 14c can operate at the same frequency as driven by synchronous signals fed from the control elements 11a, 11b and 11c via the driving channel 12a, 12b and 12c and the first, second and third power amplification units 13a, 13b, and 13c respectively.
Timing among the control elements 11a, 11b, and 11c is controlled by the synchronous signal bus 10. As such, the IC based control elements 11a, 11b, and 11c are very complicated in the design phase for achieving the timing control purpose. To the worse, more control elements are required, as the number of lamps increases. This may further complicate the circuitry for controlling such many lamps. Also, associated components are required to operate in conjunction with IC based control elements for carrying out frequency synchronization. This can incorporate an excessive number of components in the circuitry and greatly increase the manufacturing cost. Thus, the need for improvement still exists.